Tropical Storm BORIS

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM BORIS DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP022008
800 AM PDT FRI JUN 27 2008
 
A CONVECTIVE BAND WITH CLOUD TOP TEMPERATURES TO -80C HAS DEVELOPED
AROUND THE CENTER OF TROPICAL DEPRESSION TWO-E DURING THE PAST
SEVERAL HOURS.  SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM BOTH
SAB AND TAFB...AND RE-EXAMINATION OF EARLIER SCATTEROMETER DATA
SUGGESTED 35 KT WINDS.  BASED ON THIS...THE DEPRESSION IS UPGRADED
TO TROPICAL STORM BORIS.  THE INITIAL INTENSITY IS INCREASED TO 35
KT...AND THIS MAY BE CONSERVATIVE.  THE CIRRUS OUTFLOW IS CURRENTLY
GOOD IN THE SOUTHWESTERN SEMICIRCLE AND POOR ELSEWHERE.

THE INITIAL MOTION IS 295/8. WATER VAPOR IMAGERY AND LARGE-SCALE
MODEL ANALYSES SHOW A MID/UPPER-LEVEL TROUGH OVER THE PACIFIC NORTH
OF 15N BETWEEN 115-135W.  THE MODELS FORECAST THIS TROUGH TO MOVE
WESTWARD AND WEAKEN...WITH A MID/UPPER-LEVEL RIDGE BUILDING
WESTWARD FROM MEXICO TO THE NORTH OF BORIS.  THIS EVOLUTION SHOULD
ALLOW BORIS TO MOVE WEST-NORTHWESTWARD FOR 24 HR OR SO...FOLLOWED
BY A TURN TOWARD THE WEST AS SHOWN BY THE GFS GFDL AND HWRF.  THE
FORECAST TRACK FOLLOWS THIS SCENARIO...WITH THE NEW FORECAST BEING
A LITTLE NORTH OF AND SLOWER THAN THE PREVIOUS FORECAST.  IT IS
DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE IN BEST AGREEMENT WITH THE
CORRECTED MODEL CONSENSUS.  THE ECMWF SHOWS AN ALTERNATE
SCENARIO...WITH BORIS BECOMING STATIONARY OR MOVING EASTWARD AFTER
96 HR DUE TO THE DEVELOPMENT OF ANOTHER TROPICAL CYCLONE TO THE
EAST.  WHILE ANOTHER CYCLONE IS A DISTINCT POSSIBILITY...THE ECMWF
MAY BE MAKING THE SYSTEM TOO POWERFUL AND TOO LARGE.  THUS...ITS
FORECAST TRACK FOR BORIS APPEARS UNLIKELY AT THIS TIME.

BORIS IS CURRENTLY IN AN ENVIRONMENT OF LIGHT TO MODERATE
EAST-NORTHEASTERLY VERTICAL WIND SHEAR.  THE LARGE-SCALE MODELS
FORECAST THIS PATTERN TO PERSIST FOR 24-36 HR.  AFTER THAT...THEY
FORECAST A PIECE OF AN UPPER-LEVEL TROUGH CURRENTLY OVER THE GULF
OF MEXICO TO MOVE WESTWARD AND PASS NEAR BORIS...ACCOMPANIED BY
A SIGNIFICANT INCREASE IN SHEAR.  THIS WOULD LIKELY STOP
INTENSIFICATION...SO THE INTENSITY FORECAST CALLS FOR BORIS TO
REACH A PEAK INTENSITY OF 50 KT IN ABOUT 48 HR.  THE SHEAR IS
FORECAST TO DECREASE AFTER 72 HR...BUT BY THAT TIME BORIS IS
FORECAST TO MOVE OVER COOLER SEA SURFACE TEMPERATURES.  AN
ALTERNATIVE SCENARIO BASED ON CURRENT CONVECTIVE TRENDS IS THAT
BORIS COULD STRENGTHEN FASTER THAN CURRENTLY FORECAST FOR THE FIRST
36 HR AND REACH A HIGHER PEAK INTENSITY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/1500Z 12.6N 109.3W    35 KT
 12HR VT     28/0000Z 13.0N 110.4W    40 KT
 24HR VT     28/1200Z 13.3N 111.8W    45 KT
 36HR VT     29/0000Z 13.4N 113.5W    50 KT
 48HR VT     29/1200Z 13.5N 115.2W    50 KT
 72HR VT     30/1200Z 13.5N 118.5W    50 KT
 96HR VT     01/1200Z 13.5N 122.0W    40 KT
120HR VT     02/1200Z 13.5N 125.0W    35 KT
 
$$
FORECASTER BEVEN
 
NNNN